Field of the Invention
The invention relates to a method for monitoring the corrosion of C-steel of a vessel, in particular of a steam generator, while the vessel is being cleaned using at least one chemical which releases a gas, in particular nitrogen, during the cleaning process.
When cleaning vessels, which are, for example, steam generators in a nuclear power plant, the intention is to dissolve deposits with chemicals. The deposits often include magnetite. After the deposits have been removed, suitable chemicals attack the material of the vessel. At individual locations, the chemicals often penetrate through to the material of the vessel and attack the material even before the vessel has been sufficiently cleaned. When this happens, hydrogen is released.
Various methods for detecting that the chemicals are attacking the steel of the vessel have already been proposed, including measuring the hydrogen produced by corrosion, or electrochemical measurements.
However, the known methods cannot be used to establish the extent of progress of the overall cleaning operation. If the chemical reaches the C-steel on only a relatively small part of the vessel inner wall, hydrogen is released even though most of the vessel has not yet been cleaned and is still covered, for example with magnetite.